This one's pretty nasty. Hold on to your guts.
We humans often leave food offerings for spirits and supernatural beings. You'll find a favorite beverage left at a Thai spirit house, a cup of wine for Elijah at Jewish passover and Santa of course gets Milk and Cookies.
In the folklore of Germany, there's Berchta. Older pagan traditions regarded her as a benign deity, but Christian Germany knew her as a monstrous crone (and a bit of a nursery bogey) with a vengeful need to attend your Feast of Epiphany each January 6. So be sure to set her a place at the table and serve her up a proper portion of the grub, otherwise she'll come back to claim it the hard way.
According to folk historian Carol Rose, Berchta will sniff you out in your bloated, post-feast slumber. Then she'll rip her share of the meal from your stomach and gobble it down. Finally, she'll stitch up the wound with a handheld plowshare and a length of chain. So I guess she's not a complete jerk.
Werewolves and Aliens
This monster contains several interesting elements. Food offerings aside, she's kind of like Rougarou in that she weighs in on Christian feast/fast traditions. And finally, I can't help but think about modern alien abduction accounts of strange surgeries performed in the night. However, most accounts of alien implants involve rather inconsequential scars -- the sort of marks that were likely on your body for some time before your brain needed to make all of these magical connections.
So it really has more in common with urban legends about waking up in a Mexican cooler with a stitched-up side and a note about your missing kidney.
Monster of the Week is a - you guessed it - regular look at the denizens is of our monster-haunted world. Sometimes we'll focus on the cultural aspects, but mostly we'll look at the possible science behind a creature of myth, movie or legend.